TEMPE, Ariz. — A star in deep space is giving new meaning to the saying “here today, gone tomorrow.” Astronomers have witnessed the fastest star explosion ever recorded from Earth.
They watched as the white dwarf “stole” gas from a nearby red giant, triggering one of the biggest blasts ever seen — which scientists call a nova. The nova was bright enough for people to see it with binoculars around the world. However, this stellar event lasted for just over one day, which is up to three times quicker than any other to date.
Material shot into space at speeds of millions of miles an hour, which we observe as visible light. Named V1674 Hercules, the nova was visible to the naked eye for just over 24 hours before “fizzling out.”
Lead author Professor Sumner Starrfield from Arizona State University says the event on June 12, 2021 was similar to someone turning a flashlight on and off. Novas differ from supernovas. They occur in binary star systems, where small and incredibly dense stars orbit much bigger Sun-like companions.
Gas stripped from the latter spirals down to the surface of the former, like water down a bathtub drain. Heated and compacted by gravity, the hydrogen fuses and blows up like a thermonuclear bomb.
“It was only about one day, and the previous fastest nova was one we studied back in 1991, V838 Herculis, which declined in about two or three days,” Prof. Starrfield says in a university release.
The nova is still ‘ringing’ in space
The study provides new insight into the chemistry of our solar system, the death of stars, and the evolution of the universe. The nova’s speed wasn’t its only unusual trait. The light and energy sent out also pulses like the sound of a reverberating bell.
Every 501 seconds, there is a wobble detectable in visible light waves and X-rays. It is still there a year later and is set to continue for even longer.
“The most unusual thing is that this oscillation was seen before the outburst, but it was also evident when the nova was some 10 magnitudes brighter,” says Mark Wagner, head of science at the Large Binocular Telescope Observatory. “A mystery that people are trying to wrestle with is what’s driving this periodicity that you would see it over that range of brightness in the system.”
The team also noticed a strange wind as they monitored the matter ejected by the nova. It may be dependent on the positions of the white dwarf and its companion star. They appear to be shaping the flow of material into space surrounding the system which lay in the constellation of Hercules.
It is very conveniently placed, being in a dark sky in the east as twilight fades after sunset. As this places it less than 17° north of the celestial equator, it is therefore visible all over the world.
Is this how our solar system formed?
Novae can tell us important information about our solar system and even the universe as a whole. Scientists believe about 30 to 60 occur each year in the Milky Way galaxy, though they only discover about 10 during that time. Most are obscured by interstellar dust.
A white dwarf collects and alters matter, then seasons the surrounding space with new material when it goes nova. It is an important part of the cycle of matter in space. The materials ejected by novae will eventually form new stellar systems. Such events helped form our solar system as well, ensuring that Earth is more than a lump of carbon.
“We’re always trying to figure out how the solar system formed, where the chemical elements in the solar system came from,” Prof. Starrfield says. “One of the things that we’re going to learn from this nova is, for example, how much lithium was produced by this explosion. We’re fairly sure now that a significant fraction of the lithium that we have on the Earth was produced by these kinds of explosions.”
Sometimes a white dwarf star doesn’t lose all of its collected matter during a nova explosion, so with each cycle, it gains mass. This would eventually make it unstable, and the white dwarf could generate a “type 1a” supernova, which is one of the brightest events in the universe. Each type 1a supernova reaches the same level of brightness, so they are known as standard candles.
“Standard candles are so bright that we can see them at great distances across the universe. By looking at how the brightness of light changes, we can ask questions about how the universe is accelerating or about the overall three-dimensional structure of the universe,” says co-author Prof. Charles Woodward from the University of Minnesota. “This is one of the interesting reasons that we study some of these systems.”
Discovered by an amateur
Additionally, novae can tell us more about how stars in binary systems evolve, a process that is not well understood by astronomers. They also act as living laboratories where scientists can see nuclear physics in action and test theoretical concepts. The nova took the astronomy world by surprise. It wasn’t on scientists’ radar until an amateur astronomer from Japan, Seidji Ueda, discovered and reported it.
Citizen scientists play an increasingly important role in the field of astronomy, as does modern technology. The nova described in the Research Notes of the American Astronomical Society is now too faint for other types of telescopes to see. However, it can still be monitored by the Large Binocular Telescope thanks to its wide aperture and state of the art scanners.
Prof. Starrfield and colleagues now plan to investigate the cause, the processes that led to it, the reason for its record-breaking decline, the forces behind the observed wind, and the pulsing brightness.
South West News Service writer Mark Waghorn contributed to this report.